The present invention relates generally to control systems for use in motor vehicles, and more particularly to control systems equipped with a malfunction detecting device for checking the abnormality of instruments such as an analog-to-digital converter (which will hereinafter be referred to as an A/D converter) and various sensors.
For control of a motor vehicle, an electronic control unit generally comprising a microcomputer is responsive to the output signals of various sensors after converted into the corresponding digital signal through an A/D converter. When the value of the reception signal shows an abnormality, that is, when it is out of the normal range, the electronic control unit informs the user of the abnormality. There is a problem, however, in that it is difficult to identify which device is not functioning properly, i.e., whether or not the A/D converter or the sensor is abnormal, thereby preventing an effective repair or exchange of the device.